[postgis-users] How to do a cartesian projection in PostGIS (1.5)

[Kostis Kyzirakos]

Hi All!
This may be a naive question, but I am not sure how to do a cartesian
projection in PostGIS (version 1.5).
Assume that we have a table MySpatialGeometries(id integer, geo geometry),
and a tuple with id 10 and geo the rectangle  POLYGON(0 0 0,1 0 0,1 0 1,0 0
1,0 0 0).

How may I calculate the cartesian projection of the geometry along the x,y
or z axis?

For example, how can I make the following calucations:
1. project on x-axis (project out y,z), result: Linestring (0 0 0, 1 1 0)
2. project on y-axis (project out x,z), result: Point (0 0 0)
3. project on x,y axis (project out z), result: Linestring (0 0 0, 1 1 0)
4. project on x,z axis (project out y), result: Polygon(0 0 0,1 0 0,1 0 1,0
0 1,0 0 0).
etc.

I think that I can express case 3 using the Force2D function.
But how can I express the other cases?

Thanks for your help!

Cheers,
Kostis
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